5. Un secondo esperimento sulla resa visiva di sorgenti di luce
5.8 Risultati del secondo esperimento
Per lo svolgimento del secondo esperimento si è fatto uso di quattro costruzioni LEGO ™ identiche, posizionate (orientate allo stesso modo) in quattro light box, tre delle quali contenente ciascuna due sorgenti di luce da testare, mentre la quarta conteneva la luce di riferimento.
Sono stati considerati sei mattoncini colorati di: arancione, verde, rosso, bianco, blu e giallo (si veda figura 32).
In tabella 8 i risultati per le sei sorgenti di luce scelte. Totale 2 indica le medie considerando anche i dati non attendibili (considerando quindi 80 studenti).
Tabella 8: valutazioni medie da parte degli osservatori per i sei mattonicini colorati e medie totali, per le sei sorgenti di luce testate.
Arancione Verde Rosso Bianco Blu Giallo Totale Totale 2
B1S1 88.625 83.333 80.792 87.44 92 80.541 85.455 82.433 B2S1 82.75 74.166 73.521 83.208 80.125 74.854 78.104 71.308 B3S1 83.104 78.708 82.187 86.270 85.958 75.625 81.957 78.770 B1S2 82.666 89.583 72.083 81.375 86.250 74.791 81.125 79.433 B2S2 64.646 75.604 61 70.52 74.270 70.833 69.479 62.312 B3S2 88.646 90 91.75 92.021 91.979 89.979 90.729 90.177
In figura 43 gli stessi dati sono mostrati in forma grafica (dove O=orange/arancione, G=green/verde, R=red/rosso, W=white/bianco, B=blue/blu, Y=yellow/giallo, T= total/totale)
Figura 43: grafici delle medie riportati in tabella 7.
Anche in questo caso vengono riportato gli istogrammi nelle due forme (completi e approssimati alla decina, nelle figure 44-49) di tutti i dati.
Arancione Verde Rosso Bianco Blu Giallo
Arancione Verde Rosso Bianco Blu Giallo
Figura 45: istogrammi relativi all'esperimento con i lego, osservati nella Box 2, illuminanti dalla sorgente 1 (B2S1).
Arancione Verde Rosso Bianco Blu Giallo
Figura 46: istogrammi relativi all'esperimento con i lego, osservati nella Box 3, illuminanti dalla sorgente 1 (B3S1).
Arancione Verde Rosso Bianco Blu Giallo
Figura 47: istogrammi relativi all'esperimento con i lego, osservati nella Box 1, illuminanti dalla sorgente 2 (B1S2).
Arancione Verde Rosso Bianco Blu Giallo
Arancione Verde Rosso Bianco Blu Giallo
Figura 49: istogrammi relativi all'esperimento con i lego, osservati nella Box 3, illuminanti dalla sorgente 2 (B3S2).
Nel grafico di figura 50 vengono infine mostrate le medie dei punteggi di tutte le sorgenti di luce, utilizzando come i campioni le patch del Macbeth Color Checker (barre bianche) e i mattoncini LEGO™ (barre grigie).
Figura 50: a sinistra le medie dei dati considerati attendibili, a destra le medie usando anche i dati considerati non attendibili.
Dai grafici in figura 50 si nota come tenendo conto o meno dei dati considerati non attendibili, l’andamento è quasi identico, se non leggermente scalato (principalmente perché sono stati tolti gli zeri che abbassano le medie).
Da questo grafico si deduce che la sorgente di luce che si comporta meglio è quella che si trova in B3S2 (Alogena, Philips Master Classic), mentre quella che da risultati peggiori è quella denominata B2S2 nel caso dei LEGO (Century Goccia MultiLED).
Notiamo come B2S1 e B2S2 diano risultati piuttosto differenti a seconda che si stia considerando una scena 3D (LEGO ™) o 2D (Macbeth Color Checker), tuttavia, poiché non è possibile mettere in relazione l’uso di una scena 2D o 3D con la migliore percezione della resa visiva, poiché i due casi seguono due tendenze.
Conclusioni
Abbiamo voluto verificare nella pratica se e quanto l’indice di resa cromatica standard sia o meno adeguato a dare una stima della conservazione dell’apparenza cromatica. Gli esperimenti hanno confermato le riserve che il mondo scientifico nutre nei confronti di questo metodo di misura. Partendo dall’analisi delle caratteristiche del CRI standard abbiamo voluto approfondire, ed in molti casi testare, gli indici di resa cromatica alternativi che sono stati sviluppati in questi ultimi anni. Gli esperimenti condotti non avevano lo scopo di fare una classifica sulla bontà degli indici alternativi, ci interessava di più analizzare i lori principi base e le loro caratteristiche nel tentativo di disegnare un indice di resa cromatica più completo, che considerasse anche la distribuzione della luce nella scena, non solo le sue caratteristiche spettrali. Siamo infatti convinti che la configurazione della scena possa influenzare notevolmente l’apparenza cromatica. Abbiamo quindi investigato le misure del contrasto percettivo sviluppate finora e le abbiamo testate nel tentativo di poterle applicare in un CRI che tenga conto anche delle caratteristiche visive della scena da illuminare.
Una delle direzioni di ricerca da percorrere è senz’altro quella di includere negli indici di resa cromatica un modello di percezione visiva un po’ meno semplificato di quelli usati oggi. Un esperimento preliminare in questo senso è stato presentato nel capitolo 3. I risultati sono ancora molto preliminari, ma riteniamo la direzione di ricerca molto promettente.
La verifiche sperimentali dei capitoli 4 e 5 hanno avuto anche lo scopo di proporre un protocollo pratico per la verifica sul campo dell’indice di resa cromatica, non solo rispetto a riflettanze opache standard, ma anche ad oggetti tridimensionali con moderate interriflessioni ed a configurazioni metameriche.
I tre aspetti del progetto, indici alternativi di resa cromatica, misure di contrasto e test sul campo, si integrano nella necessità di futura ricerca e sperimentazione per lo sviluppo di indici di resa cromatica che tengano in considerazione anche il contesto di visione.
Alla fine del report abbiamo voluto aggiungere una bibliografia estesa per aiutare il lettore in un suo eventuale percorso di approfondimento.
Tale lavoro ha dato luogo, oltre a questo rapporto, ad una pubblicazione a conferenza internazionale già accettata:
Simonetta Fumagalli, Cristian Bonanomi, Alessandro Rizzi, “An experiment on the color rendering of different light sources”, Color Imaging XVIII: Displaying, Processing, Hardcopy, and Applications, IS&T-SPIE Electronic Imaging, 3 - 7 February 2013, San Francisco (USA)
e ad altre pubblicazioni in preparazione che verranno inviate rispettivamente a: • Journal of Optical Society of America A
• Conferenza CIE per il centenario “Towards a new century of light”, 15-16 Aprile 2013, Parigi
Riferimenti bibliografici
1. CIE 17.4-1987 “International Lighting Vocabulary”, ISBN 978 3 900734 07 7. 2. C. Oleari (a cura di), “Misurare il colore”, Hoepli, 1998.
3. S. Brueckner, P. Bodrogi, T. Q. Khanh, “Colour Rendering of new white LED light sources – visual tests,” Proceedings of Lux Europa, Istanbul, 2009, pp. 397-404.
4. R. W. G.Hunt, “Light and dark adaptation and the perception of color”, J. Opt. Soc. Am.42, 1952. 5. H. Helson, D.B. Judd,M.H. Warren, “Object color changes from daylight to incandescent filament
illumination”, Illum. Eng. 47, 1952.
6. D. L. MacAdam, “A nonlinear hypothesis for chromatic adaptation”, Vis. Res. 1, 1961.
7. W. D. Wright, “Why and how chromatic adaptation has been studied,” Color Res. Appl. 6, 1981. 8. L. Mori, H. Sobagaki, H. Komatsubara, K. Ikeda, “Field trials on CIE chromatic adaptation formula”,
Proceedings of the CIE 22nd Session, Melbourne, 1991.
9. M. D. Fairchild, “Formulation and testing of an incomplete-chromatic-adaptation model”, Color Res. Appl. 16, 1991.
10. M. R. Luo, A. A. Clarke, P.A. Rhodes, A. Schappo, S. A. R. Scrivner, C.J. Tait, “Quantifying colour appearance. Part I”. LUTCHI colour appearance data, Color Res. Appl. 16, 1991a.
11. M. R. Luo, A. A. Clarke, P.A. Rhodes, A. Schappo, S. A. R. Scrivner, C.J. Tait, “Quantifying colour appearance. Part II. Testing colour models performance using LUTCHI color appearance data, Color Res. Appl. 16, 1991b.
12. R. W. G Hunt, M. R. Luo, “Evaluation of a model of colour vision by magnitude scalings: Discussion of collected results”, Color Res. Appl. 19, 1994.
13. W. Davis, Y. Ohno, “Toward an improved color rendering metric,” Proceedings of SPIE 5941, I.T. Ferguson, J.C. Carrano, T. Taguchi, and I.E. Ashdown, eds., San Diego: 2005.
14. W. Davis, Y. Ohno, “Development of a Color Quality Scale,” Proceedings of Light and Color in Lighting Research Office Symposium, 2006.
15. CIE, Colour Rendering, TC 1-33 closing remarks, CIE Pubbl. No. 135/2, 1999.
16. D. Geisler-Moroder, A. Dur, “Color-rendering indices in global illumination methods,” Journal of Electronic Imaging, vol. 18, 2009, pp. 043015-12.
17. F. Szabó, I. Zilizi, P. Bodrogi, J. Schanda, "Visual experiments on colour harmony: a formula and a rendering index", CIE 2007 Session. Beijing, China, 2007.
18. K. Smet, W.R. Ryckaert, S. Forment, W. Hertog, G. Deconinck, P. Hanselaer, “Colour rendering: an object based approach,” CIE Light and Lighting Conference with special emphasis on LEDs and Solid State Lighting, Budapest, Hungary: 2009.
19. K. Smet, S. Jost-Boissard, W. R. Ryckaert, G. Deconinck, P. Hanselaer, “Validation of a colour rendering index based on memory colours,” in CIE Lighting Quality & Energy Efficiency, Vienna, 2010, pp. 136–142.
20. O. da Pos, M. L. Pietto, “Evaluation of light sources through the unique hues and a new multisensory semantic differential”, Atti della VII conferenza Nazionale del Colore, Roma, 15-16 Settembre 2011. 21. H. Yaguchi, Y. Takahashi, S. Shioiri, “A proposal of color rendering index based on categorical color
names”. Internat. Lighting Congress, Istanbul 2001.
22. Li, C., Ronnier Luo, M., Li, C. and Cui, G. (2012), “The CRI-CAM02UCS colour rendering index”, Color Res. Appl., 37, pp. 160–167.
23. J. P. Freyssinier-Nova, M. S. Rea, "A two-metric proposal to specify the color-rendering properties of light sources for retail lighting, in Tenth International Conference of Solid-State Lighting, Proceedings of SPIE (San Diego, CA, 2010).
24. C. Oleari, “Colour Rendering Quality of a Light Source and Perceived Colour Gamut as the MacAdam Limit of the Adapted Observer CIE 31 by Perfect Colour-Constancy Actuation in a Colour-Vision Model
Based on the OSA-UCS System”, published in Atti della VII conferenza Nazionale del Colore, Roma, 15-16 Settembre 2011.
25. P. Bodrogi, S. Brückner, T.Q. Khanh, “Ordinal scale based description of colour rendering”, 2011, Color Res. Appl., 36, pp. 272–285.
26. P. Bodrogi, S. Brückner,T. Q. Khanh, “Re-defining the colour rendering index,” CIE Proceedings 2009. 27. http://cie2.nist.gov/TC1-69/Darmstadt/cie-tc-1-69-darmstadt-rcri-method-equations-2a.pdf,
consultato a Luglio 2012.
28. L. A. Whitehead,M. A. Mossman, “A Monte Carlo method for assessing color rendering quality with possible application to color rendering standards”, 2012, Color Res. Appl., 37, pp.13–22.
29. K. Hashimoto, T. Yano, M. Shimizu, Y. Nayatani, “New method for specifying color-rendering properties of light sources based on feeling of contrast”, 2007, Color Res. Appl., 32, pp. 361–371. 30. CIE, “A method of predicting corresponding colours under different chromatic and illuminance
adaptations”, CIE: Vienna, Austria; 1994. CIE Publication No. 109.
31. K. Hashimoto, Y. Nayatani, “Visual clarity and feeling of contrast”, 1994, Color Res Appl. 19, pp. 171– 185.
32. A.A. Michelson, “Studies in Optics”, University of Chicago Press, Chicago (1927).
33. P.E. King-Smith, J.J. Kulikowski, “Pattern and flicker detection analyzed by subthreshold summation”, Journal of Physiology, 249, pp. 519-548, (1975).
34. D.A. Burkhardt, J. Gottesman, “Symmetry and constancy in the perception of negative and positive luminance contrast”, Journal of the Optical Society of America A, 1, pp. 309-316, (1984).
35. P. Whittle, “Increments and decrements: luminance discrimination”, Vision Res., 26, pp. 1677-1691, (1986).
36. E. Peli, Contrast in complex images, J. Opt. Soc. Am. A., Vol. 7, No. 10, pp. 2032-2040, (1990).
37. A. J. Ahumada, Jr., B. L. Beard., “A Simple Vision Model for Inhomogeneous Image Quality Assessment”, NASA Ames Research Center, Moffett Field, CA
38. Y. Tadmor, D.J. Tolhurst, Calculating the contrast that retinal ganglion cells and LGN neurones encounter in natural scenes, Vision Research 40, 3145-3157, (2000).
39. P. Reinagel, A. M. Zador, Natural scene statistics at the center of gaze, Network: Computation in Neural Systems, 10:1—10, (1999).
40. A. Rizzi, T. Algeri, G. Medeghini, D. Marini, “A proposal for Contrast Measure in Digital Images”, CGIV04, IS&T Second European Conference on Color in Graphics, Imaging and Vision, April 5-8, 2004, Aachen (Germany).
41. J.J. McCann, “Spatial Contrast and scatter: apposing partners in sensation”s, Electronic Imaging 1999, Conference on Human Vision and Electronic Imaging IV, pp. 97-104, San Josè, USA, 1999.
42. G. Simone, M. Pedersen, J. Y. Hardeberg, “Measuring perceptual contrast in digital images”. Journal of Visual Communication and Image Representation, 23 (2012), pp. 491-506
43. J. J. McCann, A. Rizzi “Art and Science of HDR Scene Imaging”, New York: John Wiley, 2011.
44. E. Reinhard, G. Ward, S. Pattanaik, P. Debevec, “High Dynamic Range Imaging”, Morgan Kaufmann, 2005.
45. A. Rizzi, J.J. McCann, “On the behavior of spatial models of color”, IS&T/SPIE Electronic Imaging 2007, S.Josè (California – USA), 28 gennaio – 1 febbraio 2007
46. E. Provenzi, M. Fierro, A. Rizzi, L. De Carli, D. Gadia, D. Marini, “Random Spray Retinex: a new Retinex implementation to investigate the local properties of the model”, IEEE Transactions on Image Processing, Vol. 16, Issue 1, pp. 162-171, 2007.
47. E. Land and J. McCann, “Lightness and Retinex Theory”, J. Opt. Soc. Am. 61(1), 1–11 (1971).
Bibliografia estesa
48. M. Abe, H. Ikeda, Y. Higaki, and M. Nakamichi, “A method to estimate correlated color temperatures of illuminants using a color video camera,” IEEE Transactions on Instrumentation and Measurement, vol. 40, 1991, pp. 28-33.
49. ASSIST, “Recommendations for Specifying Color Properties of Light Sources for Retail Merchandising,” Alliance for Solid-State Illumination Systems and Technologies, vol. 8, 2010.
50. K. Bieske, P. Csuti, and J. Schanda, “COLOUR APPEARANCE OF METAMERIC LIGHTS AND POSSIBLE COLORIMETRIC DESCRIPTION,” CIE Expert Symposium on Visual Appearance, 2007, pp. 137-139. 51. N. Bo, P. Iacomussi, and G. Rossi, “On the LED Colour Rendering Evaluation for works of art lighting,”
Proceedings of 11th Lux Europa, Istanbul: 2009, pp. 405-410.
52. P. Bodrogi, S. Brückner, and T.Q. Khanh, “Effect of Inter-observer Variability of Colour Vision on the Colour Quality of Modern Light Sources,” Proceedings of Lux Europa, Istnbul: 2009, pp. 393-396. 53. C. Chain, D. Dumortier, and M. Fontoynont, “A Comprehensive Model of Luminance, Correlated
Colour Temperature and Spectral Distribution of Skylight: Comparison With Experimental Data,”
Solar Energy, vol. 65, Apr. 1999, pp. 285-295.
54. A.N. Chalmers, S. Soltic, Towards the Optimum Light Source Spectrum, Advances in OptoElectronicsVolume 2010 (2010), Article ID 596825, 9 pages
55. C.-H. Chang, C.-C. Chen, C.-C. Wu, S.-Y. Chang, J.-Y. Hung, and Y. Chi, “High-color-rendering pure- white phosphorescent organic light-emitting devices employing only two complementary colors,”
Organic Electronics, vol. 11, Feb. 2010, pp. 266-272.
56. C.-H. Chang, K.-C. Tien, C.-C. Chen, M.-S. Lin, H.-C. Cheng, S.-H. Liu, C.-C. Wu, J.-Y. Hung, Y.-C. Chiu, and Y. Chi, “Efficient phosphorescent white OLEDs with high color rendering capability,” Organic
Electronics, vol. 11, Mar. 2010, pp. 412-418.
57. G. Cheng, M. Mazzeo, S. D’Agostino, F. Della Sala, S. Carallo, and G. Gigli, “Pure white hybrid light- emitting device with color rendering index higher than 90,” Optics letters, vol. 35, Mar. 2010, pp. 616-8.
58. Commission Internationale de l’Éclairage. CIE Pub. 177. Colour Rendering of White LED Light Sources, Vienna, 2007 (Peter Bodrogi: TC chair)
59. C. Connolly and T. Fleiss, “A study of efficiency and accuracy in the transformation from RGB to CIELAB color space,” IEEE transactions on image processing, vol. 6, Jan. 1997, pp. 1046-8.
60. T.L. Dawson, “Development of efficient and durable sources of white light,” Coloration Technology, vol. 126, Feb. 2010, pp. 1-10.
61. M. de Kok, W. Sarfert, and R. Paetzold, “Tuning the colour of white polymer light emitting diodes,”
Thin Solid Films, vol. 518, Jul. 2010, pp. 5265-5271.
62. M. Dyble, N. Narendran, A. Bierman, and T. Klein, “Impact of dimming white LEDs: chromaticity shifts due to different dimming methods,” in Solid State Lighting, vol. 5941 of Proceedings of SPIE, pp. 291– 299, August 2005.
63. T. Erdem, S. Nizamoglu, X.W. Sun, and H.V. Demir, “A photometric investigation of ultra-efficient LEDs with high color rendering index and high luminous efficacy employing nanocrystal quantum dot luminophores,” Optics express, vol. 18, Jan. 2010, pp. 340-7.
64. M.G. Figueiro, K. Appleman, J.D. Bullough, and M.S. Rea, “A discussion of recommended standards for lighting in the newborn intensive care unit,” Journal of Perinatology, vol. 26, Oct. 2006, p. S19- S26.
65. S. A. Fotios, “The perception of light sources of different colour properties,” PhD thesis, UMIST, Manchester, 1997.
66. M.K. Gunde, U.O. Krasovec, and W.J. Platzer, “Color rendering properties of interior lighting influenced by a switchable window,” Journal of the Optical Society of America. A, Optics, image
science, and vision, vol. 22, Mar. 2005, pp. 416-23.
67. X. Guo and K. W. Houser, “A review of colour rendering indices and their application to commercial light sources,” Light. Res. Technol. 36(3), 183–199 (2004).
68. G. He and L. Zheng, “White-light LED clusters with high color rendering,” Optics letters, vol. 35, Sep. 2010, pp. 2955-7.
69. G. He and L. Zheng, “Color temperature tunable white-light light-emitting diode clusters with high color rendering index,” Applied optics, vol. 49, Aug. 2010, pp. 4670-6.
70. K. Hirakawa and T.W. Parks, “CHROMATIC ADAPTATION AND WHITE-BALANCE PROBLEM,” IEEE
International Conference on Image Processing, 2005. ICIP 2005, IEEE, 2005, pp. III - 984-7.
71. C.-H. Hsiao, S.-W. Liu, C.-T. Chen, and J.-H. Lee, “Emitting layer thickness dependence of color stability in phosphorescent organic light-emitting devices,” Organic Electronics, vol. 11, Sep. 2010, pp. 1500-1506.
72. K.N. Hui and K.S. Hui, “Vertically-stacked LEDs with invariance of color Chromaticity,” Current Applied
Physics, vol. 11, May. 2011, pp. 662-666.
73. S. J and M. G, “Colour rendering index of led light sources,” Proc. Lumen V4 Conf., Balatonfüred: 2006.
74. S. Jost-boissard, M. Fontoynont, and J. Blanc-gonnet, “COLOUR RENDERING OF LED SOURCES : VISUAL EXPERIMENT ON DIFFERENCE , FIDELITY AND PREFERENCE,” CIE Light and Lighting
Conference with special emphasis on LEDs and Solid State Lighting, Budapest, Hungary: 2009.
75. D.B. Judd, “A Flattery Index for Artificial Illuminants,” Illum. Eng. (N.Y.) 62, 593–598, 1962.
76. E.H. Kim, K.C. Kim, D.H. Kim, J.H. Baek, and T.G. Kim, “InGaN / GaN White Light-Emitting Diodes Thin Film Phosphor,” IEEE JOURNAL OF QUANTUM ELECTRONICS, vol. 46, 2010, pp. 1381-1387.
77. S.H. Kim, Y. Jin, J.Y. Yu, J. Kim, S. Song, H. Suh, and K. Lee, “Color stable white polymer light-emitting diodes with single emission layer,” Synthetic Metals, vol. 160, Apr. 2010, pp. 835-838.
78. D.-hoon Lee, S. Park, S.-nam Park, J.-E. Lee, and Y.-wan Kim, “ARTIFACT PREPARATION FOR COMPARISON ON TOTAL LUMINOUS FLUX OF SSL PRODUCTS AMONG TESTING LABORATORIES IN KOREA,” Proceedings of CIE 2010 "Lighting Quality and Energy Efficiency", 2010, pp. 839-841.
79. Z. Lei, G. Xia, L. Ting, G. Xiaoling, L. Qiaoming, and S. Guangdi, “Color rendering and luminous efficacy of trichromatic and tetrachromatic LED-based white LEDs,” Microelectronics Journal, vol. 38, Jan. 2007, pp. 1-6.
80. K.C. Lin, “Approach for optimization of the color rendering index of light mixtures.,” Journal of the
81. J.M.M. Linhares, P.E.R. Felgueiras, P.D. Pinto, and S.M.C. Nascimento, “Colour rendering of indoor lighting with CIE illuminants and white LEDs for normal and colour deficient observers.,” Ophthalmic
& physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists), vol.
30, Oct. 2010, pp. 618-25.
82. M.R. Luo, G. Cui, and B. Rigg, “The development of the CIE 2000 colour-difference formula: CIEDE2000,” Color Research & Application, vol. 26, Oct. 2001, pp. 340-350.
83. M. López, M. Lindemann, N. Betzhold, M. Dämmig, and A. Sperling, “AGING OF PHOTOMETRIC AND COLORIMETRIC QUANTITIES OF HIGH-POWER LEDs,” CIE Proceedings Budapest, Hungary: 2009. 84. W. Ma, Z. Shi, and R. Wang, “Luminescence properties of full-color single-phased phosphors for
white LEDs,” Journal of Alloys and Compounds, vol. 503, Jul. 2010, pp. 118-121.
85. J.M. Maciel Linhares, P.D. Araújo Pinto, and S.M. Cardoso Nascimento, “Color rendering of art paintings under CIE illuminants for normal and color deficient observers.,” Journal of the Optical
Society of America. A, vol. 26, Jul. 2009, pp. 1668-77.
86. E. Mahler, J.-J. Ezrati, F. Viénot, Testing LED Lighting for Colour Discrimination and Colour Rendering, Color Research and Application 34 (2009) 8-17.
87. R. Mccluney, “Color-rendering of daylight from water-filled light pipes,” Solar Energy Materials, vol. 21, Dec. 1990, pp. 191-206.
88. N. Narendran, “Requirements for Solid-state Lighting,” Conference on Lasers and Electro-Optics
(CLEO) ., 2004, pp. 7120-7120.
89. N. Narendran and L. Deng, “Color rendering properties of LED light sources,” Solid State Lighting II :
Proceedings of SPIE, SPIE, 2002, pp. 61-67.
90. D. Nickerson, “Light Sources and Color Rendering,” Journal of the Optical Society of America, vol. 50, Jan. 1960, pp. 57 - 69.
91. Y. Ohno, “Color rendering and luminous efficacy of white LED spectra,” Fourth International
Conference on Solid State Lighting. Proc. of SPIE Vol 5530, I.T. Ferguson, N. Narendran, S.P. Denbaars,
and J.C. Carrano, eds., SPIE, 2004, pp. 88-98.
92. Y. Ohno, “CIE Fundamentals for Color Measurements,” IS&T NIP16 Intl. Conf. on Digital Printing
Technologies, Vancouver, Canada: 2000, pp. 540 - 545.
93. N. Ohta and G. Wyszecki, “Designing illuminants that render given objects in prescribed colors,”
Journal of Optical Scoiety of America, vol. 66, 1976, pp. 269-275.
94. G. Paschos, “Perceptually uniform color spaces for color texture analysis: an empirical evaluation,”
IEEE Transactions on Image Processing, vol. 10, Jun. 2001, pp. 932-937.
95. A. Pawlak and K. Zaremba, “LED Luminaire with Adjustable Colour Temperature,” Proceedings of Lux
Europa, Istanbul: 2009, pp. 215-220.
96. E. Perales, F. Martínez-verdú, and V. Viqueira, “New contributions for the revision of colour rendering for light sources based on the colour gamut volume,” En: Ciencia y tecnología del color :
Seminario de la Red Temática, celebrado en Granada los días 18 y 19 de abril de 2007, Madrid: Red
Temática "Ciencia y Tecnología del Color", 2007, pp. 1-4.
97. M. R. Pointer, “Measuring colour rendering—a new approach,”, Light. Res. Technol. 18(4), 175–184, 1986.
98. M. Rea, J. P. Freyssinier, Color rendering: Beyond pride and prejudice. Color Research and Application, 35 (2010) 401–409.
99. AR. Robertson, “Computation of Correlated Color Temperature and Distribution Temperature,”
Journal of the Optical Society of America, vol. 58, 1968, pp. 1528-1535.
100. N. Sándor, P. Bodrogi, P. Csuti, B. Kránicz, J. Schanda, “Direct visual assessment of colour rendering, In: Proceedings of the 25th session of the CIE”, San Diego, 2003, Vol.1, Part 1. D1, pp. 188-191. 101. N. Sándor and J. Schanda, “Visual Colour-rendering experiments,” AIC Colour 05 - 10th Congress of
the International Colour Association, Granada: 2005, pp. 511-514.
102. N. Sandor and J. Schanda, “Visual colour rendering based on colour difference evaluations,” Lighting Research and Technology, vol. 38, no. 3, pp. 225–239, 2006.
103. R. Saraiji, “STREETLIGHTING UNIT POWER DENSITY,” Proceedings of CIE 2010 "Lighting Quality and
Energy Efficiency", Vienna, Austria: 2010, pp. 830-838.
104. J. Schanda, “CIE Standards for assessing quality of light sources,” 1998, pp. 1-11.
105. J.D. Schanda, “Implications of vision research on luminescence investigation,” Journal of
Luminescence, vol. 24-25, 1981, pp. 851-860.
106. J. Schanda and N. Sandor, “Colour Rendering , Past – Present – Future,” International Lighting and
Colour Conf., Cape Town: 2003, pp. 1-9.
107. J. Schanda, “COLOUR RENDERING OF LIGHT SOURCES,” Colorimetry: Understanding the CIE System, J. Schanda, ed., Wiley, 2007, pp. 207-215.
108. J. Schanda, “CIE RECOMMENDATIONS AND STANDARDS ON COLORIMETRY , WHAT NEXT ?,” CIE
Symposium - 75 years of CIE Colorimetry, Ottawa: 2006.
109. B.N. Schenkman and L.T. Kjellhahl, “Preferred colour temperature on a colour screen,” Displays, vol. 20, Aug. 1999, pp. 73-81.
110. K. Schulmeister, “REVISIONS OF THE INTERNATIONAL SAFETY LIMITS FOR OPTICAL RADIATION,”
Proceedings of CIE 2010 "Lighting Quality and Energy Efficiency", Vienna, Austria: 2010, pp. 842-844.
111. T. Seim, “In search of an improved method for assessing the colour rendering properties of light sources,” Light. Res. Technol. 17 1 ,12–22, 1985.
112. C. Shen, Y. Yang, S. Jin, J. Ming, H. Feng, and Z. Xu, “White light-emitting diodes using blue and yellow–orange-emitting phosphors,” Optik - International Journal for Light and Electron Optics, vol. 121, Sep. 2010, pp. 1487-1491.
113. K. Smet, W.R. Ryckaert, S. Forment, W. Hertog, G. Deconinck, and P. Hanselaer, “COLOUR RENDERING : AN OBJECT BASED APPROACH,” CIE Light and Lighting Conference with special